CH. vii] Sulphate of Ammonia 133 



It was not obtainable by farmers during the war. b^lt 

 it is likely to be produced in great quantities in the near 

 future as considerable improvements in the process of 

 manufacture have taken place. 



Sulphate of ammonia 



This substance is manufactured from coal. The 

 potential supply is enormous: a ton of coal contains 

 on an average some 25 lbs. of nitrogen, equivalent to 

 just over 1 cwt. of sulphate of ammonia. Unfortunately 

 most of our coal is burnt under such conditions that the 

 nitrogen is lost, but in certain industries, especially in 

 the manufacture of coal gas, of producer gas, in coking 

 ovens, etc., special recovery methods are used and 

 sulphate of ammonia is obtained as a by-product^. The 

 world's output in 1913 was well over one and a quarter 

 million tons, this being nearly three times the quantity 

 produced in 1903. The process is not costly and it seems 

 capable of considerable extension . By far the largest pro- 

 spective supply, however, is that obtainable direct from 

 the air by the Haber process, in which gaseous nitrogen 

 and hydrogen are brought together under pressure and 

 at a certain not very high temperature in presence of a 

 catalyst. They then unite to form ammonia which can 

 be passed into sulphuric acid and converted into 

 ammonium sulphate, or else oxidised by the Ostwald 

 process to nitric acid, which then can be converted into 

 sodium nitrate, calcium nitrate or ammonium nitrate. 

 These processes have developed enormously during the 



^ For details of the recovery methods see art. "Ammonia" in Thorpe's 

 Dictionary of Applied Chemistry. In gasworks one ton of coal yields on 

 the average 22'7 lbs. sulphate of ammonia: in the Mond producer gas 

 plant it yields 75 to 85 lbs. 



